The root, the source of Radix Pyrethri, was used as a rubefacient and is a powerful irritant to the skin (Anon 1884). Nadkarni (1976) also notes that the root is powerfully irritant. The flower heads are dried in the sun and powdered between the thumb and fingers to produce a kind of pyrethrum (see Tanacetum cinerariaefolium Schulz-Bip). Dermatitis can occur on the hands of persons who handle the plant material (Chopra et al. 1958).

The roots of the plant contain sesamin (Burden & Crombie 1969), which is one of the compounds involved in sesame oil (Sesamum indicum L., fam. Pedaliaceae) contact dermatitis.

In traditional Western medicine, preparations of the plant have been applied as a fomentation to bruises (Remington et al. 1918).

Anaphalis morrisonicola Hayata

The potentially allergenic sesquiterpene lactone helenalin has been reported from this species (Fischer et al. 1979).

Angianthus tomentosus Wendl.

The potentially allergenic sesquiterpene lactone xanthinin has been reported from this species (Fischer et al. 1979).

Anisopappus davyi S.Moore

This species can hyperaccumulate cobalt from soils rich in this element. A concentration of 2650 ppm of cobalt in the dried plant material was detected in a specimen growing in the region of a copper and cobalt mine in the "copper belt" of Zaïre (Malaisse et al. 1979). The contact sensitising properties of cobalt and its salts are well documented (Malten et al. 1976, Cronin 1980).

Anthemis arvensis L.

Corn Chamomile

Vesicular dermatitis produced as a result of picking the plant was described by Fivoli (1936). Patch tests were positive to the flowers, and negative to the leaves. However, in three other cases, Möslein (1963) obtained positive reactions to both petals and leaves. Cross-sensitivity to two other plants named chamomile (Anthemis nobilis L. - see Chamaemelum nobile All. - and Matricaria chamomilla L. varrecutita Grierson) was also observed. Fernandez de Corres & Corrales Torres (1978) report that cross-sensitivity reactions between Anthemis arvensis and liverworts of the genus Frullania Raddi (fam. Jubulaceae) may also be observed.

Sixteen farm workers developed a bullous eruption of exposed parts (Grichener 1935); the hands and also the feet were affected in harvest workers who worked barefoot (Krantz 1938). Bullous dermatitis of the feet occurred in flax workers who worked barefoot on fields in which Anthemis cotula was growing as a common weed (D'Agostino 1927). The plant is also probably allergenic since 5 of 25 patients who had "weed dermatitis" showed positive patch test reactions to an extract of the plant (Mackoff & Dahl 1951). Shelmire (1940) observed urticarial patch test reactions lasting 12–14 h, and negative at 24 h; a 1+ patch test reaction to the "plant oil" from this species in a single patient with multiple allergies was reported by Lovell et al. (1955).

Phytophotodermatitis from the plant has been alleged; however, sunlight is not necessary to produce the skin reactions (Woods 1962). Extracts of the plant were found to have weak phototoxic activity against only one of three test micro-organisms (Wat et al. 1980b). Thune & Solberg (1980) observed positive patch test reactions to the oleoresin from this species in three photosensitive and lichen allergic patients. Frain-Bell & Johnson (1979) observed positive patch test reactions to the oleoresin of the species in 10 from 55 patients with the photosensitivity dermatitis and actinic reticuloid syndrome.

A potentially allergenic sesquiterpene lactone has been isolated from this species.

Anvillea garcini DC.

9-Hydroxyparthenolide, a potentially allergenic sesquiterpene lactone (Mitchell & Dupuis 1971), has been isolated from this species (Tyson et al. 1981).

Anvillea garcini DC. sspradiata Anderb.

(syn. Anvillea radiata Cosson & Durieu)

In NW Moroccan traditional medicine, a decoction of the flower is used externally as a vaginal antiseptic (Merzouki et al. 2000).